Are they hard-shelled or leathery. If leathery then they are snake or turtle eggs. If they are hard-shelled then they belong to a bird of some sort.

You might want to either put them back or build a make-shift incubator for them.

There aren't really any wild snakes or turtles in the UK

On a serious note, I suspect finch or swallow eggs. Mind washing them a little with water to get the dirt off and photographing them from closer up on a white sheet? Perhaps put some reference object next to them, a ruler or a coin.

On a serious note, I suspect finch or swallow eggs. Mind washing them a little with water to get the dirt off and photographing them from closer up on a white sheet? Perhaps put some reference object next to them, a ruler or a coin.

Actually, we do have a few snakes, turtles and lizards

Although, I think the turtles are a recent thing. Snakes and Lizards are a definite though